The present invention relates to a filter assembly for removing impurities from a liquid and, more particularly, to an activated carbon drinking water filter of the type especially adapted to be used in conjunction with a pitcher for receiving and dispensing the filtered water.
It is known in the prior art to utilize small activated carbon filters to treat drinking water in order to improve or eliminate undesirable taste and/or odor caused by dissolved minerals, organic chemicals and the like. Such filter will also remove sediment and colloidal particles. It is also known to provide such filters with an upper reservoir for water to be treated such that the reservoir and filter can be placed on a pitcher for receiving and dispensing the filtered water. Such assemblies are sometimes referred to as pour-through pitcher filters because they rely on gravity flow of the water from the reservoir to the pitcher via the filter. As presently known to applicants, the pour-through carbon filter elements currently available all utilize granular activated carbon as the filter media. The granular carbon is packed into and retained in an appropriate enclosure, typically including upper and lower screens having a mesh size sufficiently small to retain the granular filter material therein. The cartridge or canister of granular activated carbon may be separately removable from the reservoir for replacement or may be formed as an integral part of the reservoir so that the combination of the reservoir and filter cartridge are replaced together.
Typically, the filter cartridge containing granular activated carbon occupies a relatively large volume in order to provide adequate efficiency in the removal of contaminants and to provide an adequate filtering life before replacement is necessary. The relatively large volume of granular carbon which is required results in a typically bulky construction in prior art pour-through filters. As a result, the size of the pitcher typically used with the filter may have to be increased, reduction in the usable volume of the pitcher may have to be accepted, or a larger reservoir/filter element combination resting atop the pitcher may have to be tolerated. In addition, granular carbon filter cartridges are known to be subject to channeling in use, resulting in inadequate residence time and loss of filtering capability. Also, with a loose granular filter material, it is possible to disrupt the upper portion of the bed when water is poured into the reservoir.
Prior art pour-through pitcher filters are shown, for example, in U.S. Pat. Nos. 4,306,971; 4,895,648 and 4,969,996. Each of the filters disclosed in the foregoing patents utilizes a filter element comprising a particulate filter media such as granular activated carbon. As a result, each of the disclosed prior art constructions possesses one or more of the disadvantages mentioned above.